Because if they don't finish the game and complete all the sidequests then people will whine about it "You didn't play the whole game, you got no say on whether the game's good or not bigot".
The original point of an angry reviewer was that you have just bought a game and/or only had the budget to rent one game that week so you were stuck with it if you had something shitty to play.
Now game reviewers just get free copies of games to review, so it makes no sense.